pub fn dp_rec_mc(amount: u32) -> u32 {
    // 贪心
    let money = vec![1, 2, 5, 10, 20, 30, 50, 100];
    let mut res = 0;
    let mut idx = money.len() - 1;
    let mut myamount = amount;

    while myamount > 0 {
        let m = money[idx];
        if  myamount >= m {
            res += myamount / m;
            myamount %= m;
        }
        if idx <= 0 {
            break;
        }
        idx -= 1;
    }

    res
}
